"In August of 1851, Thomas Thompson, from Missouri gathered about him a few 'disciples' living in the vicinity of Tuleberg, now Stockton, and started the first church 'Christian, Campbellite, and Disciple of Christ,' this side of the Mississippi River."

Source:  Frontispiece of  Now and Then:  an Historical Study of the Times and Events of the Stockton, California, Churches of Christ arranged in a Chronological Order  by Norman La Grand Warren  (1977, Pioneer Publ.  Co., Fresno, CA).

From Chapter 1, page 1, of the above:

'Thomas Thompson, a gospel preacher from Kentucky, along with his family, arrived in California in forty-nine by prairie schooner, stopping at Gold Run in Placer County.  Moving to Coloma, on the American River where gold was first discovered, in 1850, he operated a hotel for miners and preached to the people.  In the winter of 1850, Thomas Thompson moved his family down to Santa Clara, buying a piece of ground on the edge of this small town where they lived the rest of their lives.

'The Spring of 1851 finds Thompson on his way back to Coloma to look after his property.  Late in the summer he visited different places on his way back to Santa Clara.  Stopping in Stockton [it was formerly called Weber's settlement or French Camp; Tuleberg and/or Castoria], he inquired about Disciples of Christ and visited in their homes.  He, believing in church organization and believing in evangelism, urged them to organize a church.  On August 24, 1851, they were called together, meeting in a small house on the corner of San Joaquin and Webber.¹